l82 



Journal of Agriculture, Victoria. [lo March. 191 2. 



LONGITUDINAL SECTION 

 THROUGH THE ROOTCAP OF A 

 YOUNG WHEAT ROOT. 



In the preceding article we noted that the 

 wheat kernel consists of three distinct por- 

 tions (i) Embryo or germ (2) Protective 

 coats (3) Endosperm — the latter consisting 

 mainly of starch and serving as reserve ma- 

 terial for nourishing the young plant. 



To bring about the germination of this 

 kernel three factors are necessary, namely 

 (i) moisture, (2) air (3) warmth. Under 

 these stimulating agencies the germ soon 

 enlarges and the plumule and radicle burst- 

 ing through the pericarp form respectixely 

 the miniature stem and the root of the young 

 plant. 



The first supply of food for the young 

 plant is derived from the reserve materials 

 of the endosperm. As these reserves of 

 food, however, are insoluble in water, they 

 are manifestlv incapable of passing out of 

 the cell walls in which they are enclosed. 

 They must be brought into a condition in 

 which they may diffuse readily from cell to 

 cell. This transformation is effected by 

 the chemical activity of a substance called 

 diastase, which is secreted by the epithelial 

 cells of the scutellum {vide p. 99, Fig. 3). 

 Diasta.se belongs to a class of bodies called unorganized ferments or 

 :-'nzymes and a very small amount of diastase is able to transform prac- 

 tically .an unlimited " '» 

 amount of starch into a * -.^ 

 soluble form. It is 

 diastase which is re- 

 sponsible for the con- 

 version of the starch of 

 the germinating barley 

 grain into maltose — 

 one of the sugars — in 

 the manufacture of 

 iBalt. This diastase 

 transforms the starch 

 of the grain into mal- 

 tose which being 

 soluble diffuses from 

 cell to cell until it 

 reaches the growing 

 points of the develop- 

 ing embryo' and sup- 

 plies it with some of 

 the nourishment neces- 

 sary to its growth. 



Similarly, the pro- 

 tein matter of the endo- 

 sperm, which, like the 



9. TRANSVERSE SECTION OF A YOUNG WHEAT 

 ROOT SHOWING ROOT HAIRS (/•//.), VASCULAR 

 BUNDLE (v.b), EPIDERMIS (('), AND GROUND 

 TISSUE. 



